The present invention relates to radio frequency transponders or tags, and more particularly to a method of assembling and housing such transponders. More specifically, the present invention relates to a method of providing a hermetically sealed package including a radio frequency transponder of the type which generally includes a coil connected to an integrated circuit and which is responsive to a received radio frequency interrogating signal to produce a radio frequency identifying signal. Transponder circuits of this type are well known in the art and, for example are shown in U.S. Pat. No. 5,099,227, issued Mar. 24th, 1992. The present invention also relates to a novel lead frame for use in the method.
Transponders of the type to which the present invention is directed are relatively small in size and are utilized for many applications, for example the access cards used for security systems to permit entry to a protected building, or to identify a particular object to which the transponder or tag is attached. In the past, such transponders were assembled and packaged in a number of different configurations. For example, the transponder electronics including the integrated circuit and the coil (and possibly a capacitor) were sealed in a glass tube, or were potted within an enclosure. A further method was to enclose the transponder electronics in a housing formed of two non-metallic housing parts which were fitted together and then welded and/or glued to form the housing. While all of these housing methods are satisfactory for various applications, the above-mentioned type packages are either unsatisfactory or are too expensive for other applications. For example, one use for such transponder devices is to attach same to articles of clothing or other textile-like materials, for example towels or sheets etc., which are to be cleaned and/or washed so as to facilitate identification of the owner of the particular article after the cleaning or washing process. For such applications, the transponder package must be hermetically sealed relative to water vapor, high temperature and laundering solutions, should be relatively small and preferably flat so as to be unobtrusive when permanently attached to the textile article, must be rugged relative to the laundering process, and should be relatively inexpensive. None of the previously mentioned packages satisfactorily meets these criteria.
Accordingly, it is the object of the present invention to provide an improved method of forming a packaged radio frequency identification device or transponder wherein the package is hermetically or environmentally sealed in a relatively simple manner.